Etching apparatus and etching method thereof

ABSTRACT

An etching apparatus and an etching method thereof are provided. An end point detector detects a light intensity at a specific wavelength for light generated when an etching process is performed on a material to be processed, and generates an end point detection signal. The material to be processed includes a material layer and at least one mask layer formed on the material layer. A control device determines an etching completion time of the mask layer according to the end point detection signal, calculates a thickness of the mask layer according to the etching completion time, and adjusts an etching time of the material layer according to the thickness of the mask layer.

BACKGROUND Technical Field

The disclosure relates to a semiconductor device, and particularlyrelates to an etching apparatus and an etching method thereof.

Description of Related Art

Through the development of semiconductor manufacturing processes inrecent years, the demands for integration level and performance ofdevices have become much higher, and plasma technologies play anessential role in the field of semiconductor manufacture. The plasmatechnology, which forms plasma by exciting a processing gas, is appliedin various semiconductor manufacturing processes, such as the depositionprocess (e.g., chemical vapor deposition), the etching process (e.g.,dry etching), etc. As semiconductor devices are being scaled down andcircuit complexity thereof is increasing, a mask film has become moreand more complicated, and the aspect ratio of a feature structure formedthrough etching correspondingly increases. Thus, the requirement for theprecision of a plasma process has become much stricter.

In the conventional art, it is common to dispose a light source in anetching chamber to emit a light beam onto an etched substrate. Byanalyzing the spectrum of reflected light from the etched material, theinformation about etching depth is obtained, so as to determine whethera target etching end point is reached. Nevertheless, as the aspect ratioof the feature structure on the etched substrate increases, it becomesmore difficult for the reflected light to form a complete interferencefringe. As a result, an error may easily occur in determining theetching end point, which as a consequence influences the precision ofthe semiconductor manufacturing process.

SUMMARY

Embodiments of the disclosure provide an etching apparatus and anetching method thereof capable of increasing the precision of asemiconductor manufacturing process.

An etching apparatus according to an embodiment of the disclosureincludes an etching device and a control device. The etching deviceperforms an etching process on a material to be processed to form afeature structure. The etching device includes an end point detector,detecting a light intensity at a specific wavelength for light generatedwhen the etching process is performed on the material to be processedand generating an end point detection signal. The material to beprocessed includes a material layer and at least one mask layer formedon the material layer. The etching device also includes a controldevice, coupled to the etching device and determining an etchingcompletion time of the mask layer according to the end point detectionsignal, calculating a thickness of the mask layer according to theetching completion time, and adjusting an etching time of the materiallayer according to the thickness of the mask layer.

Another embodiment of the disclosure provides an etching method of anetching apparatus for performing an etching process on a material to beprocessed to form a feature structure. The etching method includes stepsas follows. A light intensity at a specific wavelength is detected forlight generated when the etching process is performed on the material tobe processed, and an end point detection signal is generated. Thematerial to be processed includes a material layer and at least one masklayer formed on the material layer; An etching completion time of themask layer is determined according to the end point detection signal. Athickness of the mask layer is calculated according to the etchingcompletion time. An etching time of the material layer is adjustedaccording to the thickness of the mask layer.

Based on the above, in the embodiments of the disclosure, the etchingcompletion time of the mask layer is determined according to the endpoint detection signal, the thickness of the mask layer is calculatedaccording to the etching completion time, and the etching time of thematerial layer is adjusted according to the thickness of the mask layer.By calculating the thickness of the mask layer according to the etchingcompletion time of the mask layer, the thickness of the mask layer canbe precisely determined. Consequently, the progress of the etchingprocess on the material layer can be precisely determined. Thus, theprecision of the semiconductor manufacturing process can be effectivelyfacilitated.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments of thedisclosure and, together with the description, serve to explain theprinciples of the disclosure.

FIG. 1 is a schematic diagram illustrating an etching apparatusaccording to an embodiment of the disclosure.

FIG. 2 is a schematic view illustrating a material to be processedaccording to an embodiment of the disclosure.

FIG. 3 is a schematic view illustrating a material to be processedaccording to another embodiment of the disclosure.

FIGS. 4A to 4C are schematic diagrams illustrating relationship curvesbetween etching times of mask layers and corresponding etchedthicknesses.

FIG. 5 is a schematic view illustrating a relationship curve between acompensation time for etching a material layer and a thicknessdifference according to an embodiment of the disclosure.

FIG. 6 is a flowchart illustrating an etching method of an etchingapparatus according to an embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

FIG. 1 is a schematic diagram illustrating an etching apparatusaccording to an embodiment of the disclosure. Referring to FIG. 1, anetching apparatus 100 includes an etching device 102 and a controldevice 104. The etching device 102 is coupled to the control device 104.The etching device 102 performs an etching process on a material 108 tobe processed to form a feature structure on the material 108 to beprocessed. As shown in FIG. 2, the material 108 to be processed mayinclude a photoresist layer 202, a mask layer 204, and a material layer206. The mask layer 204 is formed on the material layer 206, and thephotoresist layer 202 is formed on the mask layer 204. In someembodiments, the photoresist layer 202 may be patterned by performing aphotolithography process, for example, so that the photoresist layer 202is provided with a feature pattern. In addition, by using thephotoresist layer 202 provided with the feature pattern as a mask, themask layer 204 and the material layer 206 are etched to form a featurestructure. In some embodiments, the material layer 206 may be anelemental semiconductor substrate (e.g., a silicon substrate or agermanium substrate) or a compound semiconductor substrate (e.g., asilicon carbide substrate or a GaAs substrate). In some embodiments, themask layer 204 may be formed by a dielectric material. Examples of thedielectric material include SiO, SiN, SiON, etc.

In the embodiment, the etching device 102 may be, for example, a plasmaetching device. However, the disclosure is not limited thereto. Morespecifically, the etching device 102 may include an etching chamber R1,an etching gas generator N1, and an end detector 106. The etchingchamber R1 may accommodate the material 108 to be processed. As shown inFIG. 1, the material 108 to be processed may be placed on a base B1 inthe etching chamber R1. The etching gas generator N1 may generate anetching gas to the etching chamber R1, so as to generate a plasma withwhich an etching process is performed on the material 108 to beprocessed. The end point detector 106 may detect a light intensity at aspecific wavelength for light generated when the material 108 to beprocessed is etched, and generates an end point detection signal. Forexample, in the embodiment, the end point detector 106 may detect thespectrum of light emitted from the plasma during the plasma etchingprocess. As the spectrum may change significantly when differentmaterial layers are etched, the end point detection signal generated bythe end point detector 106 may correspondingly exhibit changes in signalintensity, which indicate whether the etching end point is reached.

The control device 104 may be a computer or other electronic deviceswith computing capabilities. However, the disclosure is not limitedthereto. The control device 104 may determine the etching completiontime of the mask layer 204, i.e., the time required for the mask layer204 to be etched to the end point (material layer 206), as shown on theright side of FIG. 2, according to the end point detection signal Thecontrol device 104 may calculate the thickness of the mask layer 204according to the etching completion time of the mask layer 204. Forexample, the control device 104 may multiply the etching completion timeof the mask layer 204 by the etching rate of the mask layer 204 toderive the thickness of the mask layer 204. The etching rate of the masklayer 204 may be obtained by, for example, collecting data throughconventional experimentation. The thickness change of the mask layer 204also changes the aspect ratio of the feature structure formed on thematerial 108 to be processed, and the etching time required to etch thesame depth in the material layer 206 differs as the aspect ratiodiffers. Therefore, the thickness changes of the mask layer 206 maycorrespond to different etching times of the material layer 206. Afterobtaining the thickness of the mask layer 204, the control device 104may adjust the etching time of the material layer 206 according to thethickness of the mask layer 204 to prevent the thickness of the masklayer 204 from being changed due to a manufacturing factor or otherfactors, which leads to under-etching or over-etching of the materiallayer 206. Besides, unlike the conventional art which requires anadditional light source in the etching chamber so as to obtain theinformation of the etching depth by analyzing reflected light, theetching apparatus of the embodiment is capable of making detectiondirectly according to the light emitted from the plasma during theplasma etching process, and calculating the thickness of the mask layer204 according to the etching time. Therefore, the etching apparatusaccording to the embodiment of the disclosure is capable of accuratelyobtaining the thickness (etching depth) information of the mask layer204, thereby precisely etching the material layer 206, withoutincreasing the measurement cost or interrupting the etching process tomeasure the etching depth.

More specifically, the control device 104 may calculate a thicknessdifference according to the thickness of the mask layer 204, such assubtracting the default thickness (e.g., standard thickness) of the masklayer 204 from the calculated thickness of the mask layer 204 to obtainthe thickness difference (i.e., the thickness change value of the masklayer 204), and adjust the etching time of the material layer 206, suchas adding or reducing a compensation time to or from the etching time,according to the thickness difference, so as to ensure the materiallayer 206 to be etched to a predetermined depth. The relationshipbetween the thickness difference and the compensation time for etchingthe material layer 206 may be obtained by, for example, collecting datathrough regular experimentation.

In some embodiments, the material 108 to be processed may include aplurality of mask layers, instead of including only one mask layer likethe embodiment shown in FIG. 2. As shown in FIG. 3, the material 108 tobe processed may include a photoresist layer 302, three mask layers 304,306, and 308, and a material layer 310. In some embodiments, thematerial layer 310 may be an elemental semiconductor substrate (e.g., asilicon substrate or a germanium substrate) or a compound semiconductorsubstrate (e.g., a silicon carbide substrate or a GaAs substrate). Insome embodiments, the mask layers 304, 306, and 308 may be formed by adielectric material. Examples of the dielectric material include SiO,SiN, SiON, etc. Similarly, the end point detector 106 may detect thespectrum of light emitted by the plasma during the plasma etchingprocess to generate the end point detection signal. For example, the endpoint detector 106 may detect the light intensities at differentspecific wavelengths respectively corresponding to different masklayers, so as to generate corresponding end point detection signals. Thecontrol device 104 may determine the etching completion times of themask layers 304, 306, and 308 according to the end point detectionsignals corresponding to the mask layers 304, 306, and 308, andcalculate the sum of the thicknesses of the mask layers 304, 306, and308 according to the etching completion times of the mask layers 304,306, and 308 and the etching rates of the mask layers 304, 306, and 308,respectively. A thickness sum H of the mask layers 304, 306, and 308 maybe calculated according to the following equation:H=RA×TA+RB×TB+RC×TC . . .   (1),wherein RA, RB, and RC respectively represent the etching rates of themask layers 304, 306, and 308, and TA, TB, and TC respectively representthe etching completion times of the mask layers 304, 306, and 308. Insome embodiments, the relationships between the etching times of themask layers 304, 306, and 308 and the corresponding etched thicknessesmay also be stored in a storage circuit of the control device 104. Afterobtaining the etching completion times of the mask layers 304, 306, and308 according to the end point detection signals, the control device 104may obtain the thicknesses of the mask layers 304, 306, and 308corresponding to the etching completion times of the mask layers 304,306, and 308 by looking up a table. FIGS. 4A to 4C are schematicdiagrams illustrating relationship curves between the etching times ofthe mask layers 304, 306, and 308 and the corresponding etchedthicknesses. As shown in FIGS. 4A to 4C, the curves corresponding todifferent mask layers have different slopes (etching rates), and etchingcompletion times TA, TB, and TC may respectively correspond tothicknesses HA, HB, and HC of the mask layers 304, 306, and 308. Thecontrol device 104 may add up the thicknesses HA, HB, and HC to obtainthe thickness sum H of the mask layers 304, 306, and 308.

Similarly, the control device 104 may subtract a sum of defaultthicknesses of the mask layers 304, 306, and 308 from the thickness sumH of the mask layers 304, 306, and 308 to obtain a thickness differenceHD (i.e., a total thickness change value of the mask layers 304, 306,and 308), and adjust the etching time of the material layer 310according to the thickness difference. For example, the storage circuitof the control device 104 may store the etching compensation time of thematerial layer 310 corresponding to the thickness difference.Accordingly, the control device 104 may obtain the etching compensationtime of the material layer 310 corresponding to the thickness differenceby looking up a table. For example, FIG. 5 is a schematic viewillustrating a relationship curve between the compensation time foretching the material layer 310 and the thickness difference according toan embodiment of the disclosure. As shown in FIG. 5, each thicknessdifference may have a corresponding compensation time. For example, thethickness difference HD of the embodiment of FIGS. 4A to 4C maycorrespond to a compensation time TD. The control device 104 may add thecompensation time TD to the etching time of the material layer 310 toensure the material layer 310 is precisely etched to an expected depth.The thickness difference HD may be a positive value or a negative value,and the corresponding compensation time TD may also be a positive valueor a negative value. In other words, the control device 104 may increaseor decrease the etching time of the material layer 310, so as toprecisely etch the material layer 310.

FIG. 6 is a flowchart illustrating an etching method of an etchingapparatus according to an embodiment of the invention. According to theabove embodiment, the etching method of the etching apparatus includessteps as follows. First of all, the light intensity at the specificwavelength is detected for the light generated when the etching processis performed on the material to be processed and the end point detectionsignal is generated (Step S602). The material to be processed includesthe material layer and at least one mask layer formed on the materiallayer. The etching process may be a plasma etching process. However, thedisclosure is not limited thereto. The etching apparatus may include anetching chamber containing the material to be processed. By generatingan etching gas and providing the etching gas to the etching chamber,plasma is generated with which the etching process is performed on thematerial to be processed. Then, the etching completion time of the masklayer is determined according to the end point detection signal (StepS604). Then, the thickness of the mask layer is calculated according tothe etching completion time (Step S606). Then, the etching time of thematerial layer is adjusted according to the thickness of the mask layer(Step S608). For example, the thickness difference of the mask layer maybe calculated according to the thickness of the mask layer, and theetching time of the material layer may be adjusted according to thethickness difference. The thickness difference may be a differenceobtained by subtracting the default thickness (e.g., the standardthickness of the mask layer) from the thickness of the mask layer.

In an embodiment having multiple mask layers, the etching completiontime of each mask layer may be determined according to the end pointdetection signal corresponding to each mask layer, and the thickness ofeach mask layer may be calculated according to the etching completiontime of each mask layer. Then, the etching time of the material layer isadjusted according to the sum of the thicknesses of the mask layers. Forexample, the thickness difference may be obtained by subtracting the sumof the default thicknesses of the mask layers from the sum of thethicknesses of the mask layers, and the etching time of the materiallayer may be adjusted according to the thickness difference.

In view of the foregoing, in the embodiments of the disclosure, theetching completion time of the mask layer is determined according to theend point detection signal, the thickness of the mask layer iscalculated according to the etching completion time, and the etchingtime of the material layer is adjusted according to the thickness of themask layer. By calculating the thickness of the mask layer according tothe etching completion time of the mask layer, the thickness of the masklayer can be precisely determined. Consequently, the progress of theetching process on the material layer can be precisely determined. Thus,the precision of the semiconductor manufacturing process can beeffectively facilitated. Besides, unlike the conventional art whichrequires an additional light source in the etching chamber so as toobtain the information of the etching depth by analyzing reflectedlight, the etching apparatus according to the embodiments of thedisclosure is capable of accurately obtaining the thickness (etchingdepth) information of the mask layer, thereby precisely etching thematerial layer, without increasing the measurement cost or interruptingthe etching process to measure the etching depth.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of thedisclosure without departing from the scope or spirit of the disclosure.In view of the foregoing, it is intended that the disclosure covermodifications and variations of this disclosure provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. An etching apparatus, comprising: an etchingdevice, performing an etching process on a material to be processed toform a feature structure, and the material to be processed comprises amaterial layer and at least one mask layer formed on the material layer,wherein the etching device comprises: an end point detector, detecting alight intensity at a specific wavelength for light generated when theetching process is performed on the mask layer to be processed andgenerating an end point detection signal; and a control device, coupledto the etching device and determining an etching completion time of themask layer to be etched according to the end point detection signal,calculating a thickness of the mask layer to be etched according to theetching completion time, and adjusting an etching time of the materiallayer according to the thickness of the mask layer to be etched, whereinthe etching process is performed on the material layer after adjustingthe etching time of the material layer.
 2. The etching apparatus asclaimed in claim 1, wherein the control device calculates a thicknessdifference according to the thickness of the mask layer and adjusts theetching time of the material layer according to the thicknessdifference.
 3. The etching apparatus as claimed in claim 2, wherein thethickness difference is equal to a value obtained by subtracting adefault thickness from the thickness of the mask layer.
 4. The etchingapparatus as claimed in claim 1, wherein the material to be processedcomprises a plurality of mask layers, the control device determines anetching completion time of each of the mask layers, calculates athickness of each of the mask layers according to the etching completiontime of each of the mask layers, and adjusts the etching time of thematerial layer according to a sum of the thicknesses of the mask layers.5. The etching apparatus as claimed in claim 4, wherein the controldevice calculates a thickness difference of the mask layers according tothe sum of the thicknesses of the mask layers, and adjusts the etchingtime of the material layer according to the thickness difference.
 6. Theetching apparatus as claimed in claim 5, wherein the thicknessdifference is equal to a value obtained by subtracting a sum of defaultthicknesses of the mask layers from the sum of the thicknesses of themask layer.
 7. The etching apparatus as claimed in claim 1, wherein thecontrol device multiplies the etching completion time of each of the atleast one mask layer by a corresponding etching rate to obtain thethickness of each of the at least one mask layer.
 8. The etchingapparatus as claimed in claim 1, wherein the etching device furthercomprises: an etching chamber, accommodating the material to beprocessed; and an etching gas generator, generating an etching gas andproviding the etching gas to the etching chamber to generate plasma withwhich the etching process is performed on the material to be processed.9. The etching apparatus as claimed in claim 1, wherein the materiallayer is an elemental semiconductor substrate or a compoundsemiconductor substrate.